Once we get to a notion of mental content, we seem to accept readily that it is absolutely private to the person who has it. We say, "Nobody else can have my headache," or "Nobody else can have my sense impression of that chair." Let us call this the thesis of absolute privacy.
(There is also a notion of mental content, in respect of which the idea of privacy would never arise. For example, anything someone thought about. If I think about the moon that is my "mental content," and you can think about it too. My question will not be about this type of "mental content.")
Question: Is there any philosophical work that discusses and questions the thesis of absolute privacy?
Just to be clear on what I am looking for, please note:
The work must accept the notion of mental content as unproblematic or usable (whether because the author believes so or for an argument's sake) and explore specifically the idea that it is absolutely private or not.
An example may be a Frege essay, in which he imagines a mind that has certain things in it and a greater mind that has all of those (numerically identical) things plus more. This would amount to saying that mental content was not absolutely private, or that there was at least no conceptual impossibility in the idea of two minds sharing it. (I am not saying Frege was advancing this view. He mentioned something like it very briefly somewhere.)
A discussion of unusual brain configurations, such as two brains sharing some neural paths, may not qualify as an example if it avoids using the notion of mental content or uses it only to facilitate statement and disavows any kind of ontological commitment.
I am mostly interested in works in the analytic tradition. ("Analytic" here is a label sometimes contrasted with "Continental." If you don't know exactly who is analytic in this sense, you probably can't give me what I am looking for.)
Never mind Wittgenstein's private language argument. Of course, a work on it might go into what I am looking for.
I don't want to know the truth. I am only looking for published works on the topic.